Agronomic value of alfalfa semi-hybrids across contrasting Italian environments

Alfalfa (Medicago sativa L.) semi-hybrids of genetically distant material may display heterosis, but their agronomic value is hardly known. Our study evaluated two two-way and one three-way semi-hybrids and two synthetic varieties for 3-year herbage dry-matter yield (DMY) in four agricultural environments of Northern Italy formed by the factorial combination of irrigated or rain-fed cropping by pure stand (PS) or mixed stand (MS) with vigorous grasses to verify (1) the yield advantage of semi-hybrid material and (2) the ability of a phenotyping platform with eight managed environments used in a prior study to reproduce the population adaptive responses in agricultural environments. The semi-hybrids derived from putative heterotic populations selected from Italian germplasm, Egyptian germplasm, and a semi-erect pool from Eastern Europe, Canada, and Spanish Mielga germplasm. The three-way semi-hybrid showed wide adaptation and over 17% greater DMY than a variety selected from the Italian genetic base (set as a reference for synthetic variety breeding). The two-way semi-hybrids showed specific adaptation to the irrigated MS environment (where alfalfa was outcompeted) or PS environments that agreed with features of their exotic parent population, and over 19% greater yield than the reference synthetic variety in the environments where they were specifically adapted. The phenotyping platform reproduced largely the population × environment interaction effects across agricultural environments.